Abstract
The new INSN (Italian National Seismic Network) is a dense network of broadband
stations deployed for monitoring Italian seismicity. The network consists of 250 stations
with a typical station spacing of ~40 km. Earthquake early warning is the rapid
detection of an event in progress, assessment of the hazard it poses, and transmission of
a warning ahead of any significant ground motion. We explore the potential for using
the INSN real-time network for the purpose of earthquake early warning. We run the
ElarmS early warning methodology off-line using a data set of more than 200 events
with magnitude between 2.5 and 6.0. A scaling relation for magnitude determination
from the dominant period of the first seconds of signal following the P-onset is
developed from the dataset. The standard deviation in the magnitude estimates using
this approach is 0.4 magnitude units and all event magnitude estimates are within +/-0.75
magnitude units of the true magnitude. Given the existing distribution of seismic
stations it takes an average of 10 sec after event initiation before the P-wave has been
detected at 4 stations. If we require a detection at 4 stations before issuing the first alert
then the blind zone, within which no warning would be available, has a radius of ~37
km. The ElarmS methodology can provide a warning earlier than this but with a greater
uncertainty. An assessment of past damaging earthquakes across Italy shows that
applying ElarmS with the existing seismic network could provide warning to population
centers in repeats of past events. For example, in a repeat of the 1980 Irpinia earthquake
Naples could receive ~15 sec warning. The variations in the size of the blind zone and
warning times for different regions can be used as a guide to selecting strategic locations
for future station deployments.